Telephone



(No-Model.) A Y 2 Sheets-Sheet 1.

s. D. FIELD.

TBLI'TPHOITE.A

Nason-28. y Paten-ted oct. 31,1893.

(No Model.) V2 Sheets-Sheet 2.

s. D. FIELD. TELEPHONE.

IH IIIIIIIIIIIIIII Patented Oct. 31,1893. I

UNITED STATES i 4PATENT OFFICE.

STEPHEN DUDLEY FIELD, OF STOCKBRIDGE, MASSACHUSETTS.

TELEPHONE.

SPECIFICATION forming part of Letters Patent No. 507,728, dated October 31, 1893.

Application lerl June 30, 1893. SerialNo.479,207. (No model.)

To all whom it may concern:

Y Beit known that I, STEPHEN DUDLEY FIELD, a citizen of the United States, residing at Stockbridge, in the county of Berkshire and State of lVIassachusetts,have invented certain new and usefulrImprovements in Telephones, of which the following is a specification.

This invention relates to telephony,and has for its object to increase the induction in a magneto telephone, and render such instrument serviceable for the transmission of speech over longer distances and to increase its loudness and clearness.

In carrying out my invention I employ a plurality of diaphragme, all of which are mechanically connected to the same armature, and which are so arranged that they will always vibrate synchronously wit-h the sound Waves, and, by reason of their number, increase the mechanical effort exerted upon the magnetic conductor or armature. I also make use of a special device for equalizing the strain upon the diaphragm due to the magnetic attraction between the magnet and its armature.

The several features of novelty of my invention will be more particularly described hereinafter and will be definitely indicated in the claims appended tov this specification.

In the accompanying drawings which illustrate my invention, Figure ..1 isa View partly in section of an apparatus provided with two actuating diaphragms embodying my improvements. Fig. 2 is a detail sectional View of the armature. Fig. 3 is a perspective view of ,an apparatus provided with three controlling diaphragms. Fig. 4 is a side elevation of a portion of an instrument for equalizing the strain upon the diaphragm by the armature in the several positions of the latter; and Fig. 5 is a modiiication in which an armature may be supported upon one end and rendered -inharmonious by being placed in a horizontal position in the magnetic field.

Each diaphragm is mechanically connected with an armature l, which is pivotally mounted in a magnetic field upon a suitable support 7, the two extremities confronting the north and south poles of a magnet or magnets. The pivotal mounting should be as near as possible at the center of gravity of the armature, since by such a mode of support the armature is given a neutral vibratory rate equally responsive to vibrations of a composite character, and is rendered inharmonious so that it will not impose upon the line any electrical vibrations due to a rate of its own. As shown in the igure, a permanent magnet N, S is used, provided with soft iron pole-pieces upon which coils 2,

3 are mounted, and the armature l may be a stiff piece of soft iron of the proper crosssection to conduct the lines of force developed by the magnet N, S. The armature is poised upon needle points entering sockets at its longitudinal center, and will normally be strongly attracted by the poles of the magnet. A suitable mechanical connection is provided between one end of the armature and the diaphragm or diaphragme, which may be an inelastic cord or wire. I preferably use a plurality ot' diaphragms, and in such case each diaphragm will be connected by a cord or wire 4, 5, Fig. l, with an equalizing bar 6, whichV in turn is connected with one end of the armature.' Where more than two diaphragms are used the equalizing bar will be centrally connected with the armature, and' the connections with the diaphragms will be ymade at equal radial distances from the center. The mouth-piece will be suitably shaped so as to convey the air waves to the several diaphragms, and suitable recesses to receive the diaphragms and ca'ps to contine them in place will be provided in any convenient manner. The coils 2, 3 may be connected in series relation and have their free terminals v connected directly to line, in which case they will be wound with comparatively iine wire, so as to admit of a large number of turns in a small compass and develop an electro-motive-force of considerable tension; or they may be wound with coarser wire and be connected in the primary circuit of a local induction coil, by which the tension of the currentfmay be raised. The former method will, however, be preferred for its simplicity of construction.

To guard against actual contact between the magnet poles and.v vibratory armature, when working with great strength of polarization, I interpose in the connecting medium between the armature and the diaphragm a heel and toe lever toggle, as indicated at 9 in ICO Fig. 4, so that the diaphragms acquire a shifting mechanical advantage over the armature. rPhe nearer the armature approaches the magnet the greater the leverage which the diaphragm acquires in its control. By this means I secure a uniform strain upon the diaphragm in all positions of the armature. In lieu of the vertical arrangement shown in Figs. 2 and 3, the armature may be supported horizontally, as shown in Fig. 5, in which case it may be pivoted at one end and will in this condition, being acted upon by gravity, be equally responsive to waves of any period and will not impose upon line vibrations due to its own rate.

A marked advantage follows from the use of the independent armature 1, for the reason that such armature can be given suffi cient cross-section to carry a large number of lines of force, and the lines of force themselves will always keep it under stress and in a condition for actuation by the diaphragm or diaphragms to which it is connected. In a magneto instrument as ordinarily constructed the diaphragm is the only medium for varying the intensity of the magnetic field, and such diaphragm being necessarily very thin when made of iron, in order to respond to the sound waves, the resistance of the magnetic field is varied but a little and the induced currents are comparatively weak. lVhen, however, a mechanically connected independent armature is used, such armature may be made of any desired thickness, and any variation of its position in obedience to the movements of the diaphragm will very considerably affect the magnetic conductivity ofthe magnetic field in which it is located. The vibrating diaphragms may, of course, be made of any suitable material, whether metallic or not.

Another advantage, and one of equal importance, results from the employment ot' a plurality of diaphragms. The energy developcd bythe voice in speech is transmitted to the Whole body of air surrounding the speaker and is capable of atecting any number of diaphragms which may be brought within range of the air vibrations, just as the voice of a speaker may be heard by any number of hearers within range of his voice. It is evident, therefore, that if a plurality ot diaphragms be employed, each diaphragm will utilize part of the energy of the voice. Where but a singlel diaphragm is employed, only a small portion of the energy is utilized. It follows that if a single diaphragm can eifectively control an armature weighing ten grains, ten such diaphragms, if Working in unison, can control one weighing one hundred grains, and, assuming that ten grains of iron can carry ten lines of force, one hundred grains will carry ten times as many, and as the induced current developed by these organizations is practically proportional to the variation of resistance of the magnetic field, it will be seen that a multiplication of the diaphragms will multiply the inductive effect. The diaphragms should be so constructed that they will vibrate in perfect unison, to which end they should be made of the same diameter and thickness, so that when struck by waves of a given power they will all respond with equal promptness. It of different sizes or different thicknesses, one will lag more or less behind the others, and an indifferent eect will be realized. Suitable means may be provided, as indicated in the drawings, for adjusting the pole-pieces with reference to the armature.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is-

l. A magneto telephone comprising a plurality of diaphragms mechanically connected to an induction generator in such relation that the mechanical energy of all the diaphragms will be added together in effecting a movement of the generator, the diaphragms being equidistant from a common mouthpiece.

2. A magneto telephone provided with a plurality of diaphragms, mechanical connections between each diaphragm and an induction generator, and means for equalizing the tension upon all of the diaphragms during the operation of the telephone.

3. A magneto telephone comprising a plurality of diaphragms of equal size and resiliency, mechanical connections between the several diaphragms and a vibrating armature supported in a magnetic field, means for equalizing the tension upon all of the diaphragms during the operation of the telephone and generating coils in inductive relation to the magnetic field.

4. A magneto telephone provided with an armature supported in a magnetic field, a compensating device for equalizing the strain of said armature upon a diaphragm in all positions ot' the armature, and a coil inductively related to the magnetic held.

In testimony whereof I have hereunto subscribed my name this 28th day of June, A. D. 1893.

STEPHEN DUDLEY FIELD.

Witnesses:

F. S. AYMAR, Jr., THEO. C BURNETT.

tof;

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